146 BOTANICAL GAZETTE. 
suppose that at length the Fungus derives too little benefit to be 
able to go on; or the season during which the host plant flourishes 
is drawing to an end, 
No doubt we have in hetercecism the salvation of such a Fun- 
gus. Not only is itcarried through a dangerous period, by see 
ing relief at the hands of a second host, but—and which I believe 
to be far more important—it obtains reinvigoration by the ay: 
protoplasm with which it comes'in contact. We may not inaptly 
compare the sojourn of the Fungus on its second host, to a tp 
to the seaside, where the weary and enfeebled organism en)0y® 
fresh diet and associations for a time, which in their turn pall 
and prepare the recipient to renew old modes of life. 
e have seen that the disappearance of the sexual organs, 
leading to apogamy, cornmences especially in the lower Ascomy- 
cetes, and it may be more than a coincidence that epiphytic forms, 
which show a tendency to produce one kind of spore while oD — 
the living leaf and develope their asci on the fallen leaf are com- 
mon here ; such forms suggest how the parasitism and heterccis@ 
of higher forms may have begun, and it is remarkable that the 
apogamy becomes more and more complete as we ascend through 
the latter, 
velop the sexual organs in the condition typical and erfect for 
the group to which they belong. I have already referred to the 
fact that many of these forms are really saprophytes, and that 
others break down and destroy the tissues of their hosts—clum™ 
sily killing their prey, and then feeding on the rotten mass— 
have pointed out that this isa much less specialized form of para 
sitism than that of the higher Fungi and Ustilaginee. : 
Nevertheless, the sexuality shows signs of disappearance 1® 
extreme members. De Bary’ shows that in Phytophthora and ae 
a less evident passage over of protoplas® 
Peronospora there is 
from the antheridium to the oosphere than in Pythiwm ; 
In some cases, indeed, the quantity passing over is too sma 
be observed. I will not attempt to lay stress on the coincidence 
that in Phytophthora infestans (the fungus of the potato disease) 
no sexual act has yet been discovered, 
. — 
? Beitr, zur Morph., etc., der Pilze, iv, p. 72. 
